Small Engines (Lawn Mowers, etc.): Crank -- No crank, intermittent fault, partslist

Question
My MTD riding mower (model 135M679G062  14HP 42" cut) will sometimes crank, sometimes not.

The battery and the starter are good. I had them checked by a technician. I called him because it would not crank at all. He started it right up. I asked him what he did that I did not do. He wasn't sure.

After he left, I started the tractor, ran it for over an hour. I stopped and started it several times but left it running most of the time to make sure the battery would stay charged. Then I tried to start once more and got nothing. It would not crank.

I pushed it to get near an electrical outlet in case it was the battery. The battery was OK. I was stumped. Then, for some reason I decided to give it one more try,  and it started!!

While it was running I put it in the gear position that allows me to get off the seat without killing the engine. However, once I got off the seat it died. This had never happened before.

I remembered then, that I had gotten off the seat earlier to talk with my neighbor and could hear the mower engine faltering but just managing to keep running. I remember thinking that it was getting low on gas, but it was not that.

Please tell me what could be the problem, and how to check it and fix it. Thank you.  

Answer
It sounds like you may have a seat switch that's sticking or corroded and having an intermittent fault.  It should have a contact type switch, looks sort of like a leaf spring.  You can either adjust or just tie the contacts together to test it. It should be P/N 725-1303 and 725-1439 and I have them listed at $1.85 each so they're not expensive if you have to replace them and should be pretty easy to find locally.

If you need a wiring diagrasm of your mower to see how they function, there's one on my site at http://www.grandjunctionsmallengines.com/pages/parts/viewbybrand/default.aspx

Use the partslist on the right, the Quick Part Look-up, and select MTD from the brand and put your model number in the model box and the schematic will be in the parts list.

Try this and let me know if that does or doesn't help.  Thanks, PK.